D1.1 WPS allowed joint design tolerances

Date 12-12-2001 23:23

Sect. 3.13.1 seems to state, 'Dimensions of groove welds...may vary from the dimensions on the design "or" detail drawings by the amount listed in the "As Detailed" column.'
Simple enough to understand that under almost any circumstances. That's what I thought, but the section's paragraph then continues by only defining the other columns use by indicating, 'The "As Fit up" column's tolerances may 'only' be applied where the joint's dimensions are listed on the "detail" drawing.'
The latter proviso implies one "may not" use the "As Fit up" column's tolerances when the joint's dimensions are listed on the "design" drawing.
Does anyone see why AWS can't simply define the figure 5.3's columns uses by more simply stating, 'The column listing "As Fit up" tolerances may only be applied where joint dimensions are listed on the detail drawing but not if listed on the design drawing. If joint dimensions are listed on both design and detail drawings, then the "As Detailed" column's tolerances apply." ?
Have studied this blurry topic today for too long now. maybe I'm too close to the trees cause I've lost sight of the forrest and am getting dizzy and must to stop, but I'd appreciate hearing what some of the other WPS writers or users are led to believe concerning the use of the two column's tolerances.
Another obscure proviso's of D1.1 involves writing a WPS for a non-prequalified weld joint. Assumably such a WPS's listed tolerances apply only to that specific joint and no others ? In other words, if one qualifies a WPS for 'smaller than' pre-qualified root openings say for a single-vee design, expectedly the smaller root opening may not be used on any other joint designs except that single-vee ?
Does anyone else find that AWS Code users have to reach a little too much in determining the Code's intent for WPS qualifications and WPS uses ? Any supported interpretations to either of these topics would be greatly appreciated.

By MBSims

Date 12-13-2001 05:57

I don't have a copy of D1.1 handy, but I seem to recall that the "As-detailed" tolerance is the amount that the design drawings may deviate from the dimensions shown in the D1.1 prequalified details. And the "As Fitup" is the amount of deviation permitted from that shown on the design drawings. It is possible and fully acceptable to have a case where the tolerances used on the design drawing and the fitup tolerances are at their maximums and "stack up". I think there was some words in the Commentary to explain this.

This is just one of the many reasons I don't like the D1.1 Code. They have made the whole thing so complicated that it takes a Philadelphia lawyer to interpret it. I have a copy of the 1969 edition of D1.0 and it is far more practical and easier to understand and work to. Welds in structural steel are just not as complicated as the D1 committee tries to make them. It's easier to work to the ASME B&PV Code Section III requirements for nuclear reactors than it is to make a weld on a building. What's wrong with this picture?

Marty

By - Date 12-14-2001 07:33

Mr. Sims,
I don't agree with your opinion that "welds in structural steel are just not as complicated as the D1 committee tries to make them". I work on structures (floating offshore platforms) that are weight sensitive (so there is a small safety factor - i.e. thin as possible plate) and are very fatigue sensitive. In an effort to forestall fatigue cracking and failure of welds in this type of structure, the effort to qualify and apply welding procedures is quite "complicated".
I fully agree, however, that the requirements of Section 3 (Prequalification) and Section 4 (Qualification) of D1.1 are in many cases extremely difficult to interpret. The code is written the way it is because it applies to many different types of structures in many industries. To make things as easy as possible for ourselves, and seeing as the Engineer has the right and the responsibility for final acceptance/interpretation of code related issues, we always make a point of getting the Engineer's agreement on interpretational issues.
Thanks.
Mankenberg

By DGXL

Date 12-14-2001 21:39

I also disagree that structural welds are not that important. Anyone who lives in earthquake prone areas (seismic zones 3 & 4) know this all to well. Did you know many small defects deemed insignificant resulted into major failures?

A little undercut here, some underfill there = building fall down.

By MBSims

Date 12-16-2001 19:53

You both have very good points that I agree with. I didn't say structural welds are not important, they definitely are. I just don't see where such tight tolerances on groove angles make any difference in the quality of the weld or the performance of the structure. I would agree that sound engineering decisions need to be made in the selection of joint designs and parameters for the welding procedure. But again, I don't see where variables such as a change in the number of beads in a weld joint outside some tolerance band are that important. I doubt very many welders or inspectors are counting weld beads in the field to make sure the limits of this essential variable are not exceeded. This is a code that has been changed and revised so much that it does not flow well anymore and is very difficult to work with. I think they need to step back a bit and evaluate what factors are most important and how the requirements can be better organized and presented in a manner that the folks in the field can understand it and work with it better. It's kind of like the cartoon I see on jobsites that says "A zebra is a horse created by a committee."

Marty

By George-kh (**)

Date 12-16-2001 22:23

By George-kh (**)

Date 12-16-2001 22:31

Dear steveho
“As detail” column in figure 3.4 is for design and drawing. It means when you want to design or draw your joint you must follow its tolerances. D1.1-2000 page 81, double V groove weld butt joint, for example; your groove angle can be between 60 and 70 degree. Because groove angle is determined 60 degree and tolerance is +10,-0 degree.
Now, imagine the groove is designed 65 degree (it’s between 60 and 70 degree). During fit-up groove angle can be between 60 and 75 degree. Because fit-up tolerance is +10, -5 degree.

If you see all “AS fit-up” columns in figure 3.4, all fit-up tolerances are +10, -5 degree. so, it’s not obscure if you see it in figure 5.3 again. All tolerances in figure 5.3 are exactly same as figure 3.4 and they are repeated in chapter 5 for remembrance.

At last, you must follow figures 3.3 and 3.4 even for a non-prequalified joint. Because a change in theses tolerances is an essential variable (table 4.5, No.34).

Best Regards